In the late 1880s, for example, predaceous ladybird beetles imported from Australia had decimated the cottony-cushion scale insect that was consuming citrus crops in California.

The emerald ash borer is only one of the many threats to the nation's forests, which are also being attacked by the Asian longhorn beetle, gypsy moth, beech scale insect, hemlock wooley adelgid and sudden oak death fungus.

And on top of that, the crazy ants have this mutualism with a scale insect, so you can also get a dieback happening in the canopy as well.